The RTOG is a cooperative group of radiation therapy research and clinical centers organized for the purpose of conducting joint clinical investigations. The Division of Radiation Oncology of the University of Rochester Cancer Center is one of the member institutions of the RTOG and the Office of Protocol Design and of the Vice-Chairman are located within it. A listing of the major RTOG objectives and progress that has been made by the group, both nationally and at this institution, is described and includes: case accession, new research areas, standardized treatment planning, quality control, neutron clinical investigation, study registries and forms, and the interaction of the RTOG with other cooperative groups. The protocol design activities of the RTOG are reviewed through two schemes: First, major radiation themes which can apply to many disease sites: time dose factors, radiosensitizers, systemic irradiation, high LET irradiation, optimal time of radiation therapy and chemotherapy, hyperthermia, combining innovations in radiation therapy and mathemtical modeling; second, disease sites in terms of unique specific studies, especially studies of brain, lung, head and neck, genitourinary and metastatic disease. The activities of the Division of Radiation Oncology in protocol accession and the studies which are chaired by members of this institution are reviewed.